The present invention relates to a wood preservative composition based on leaching-resistant, inorganic compounds for protection of lumber, irrespective of the moisture content, against wood-damaging insects and fungi, including wood rot fungi (soft wood fungi). The lumber to be protected can be used in covered areas and also in the open, at ground level and/or exposed where constantly subjected to weathering.
Numerous inorganic wood preservatives are already known for protection of wood against damage by insects and/or fungi. Processes for introducing the preservatives into the wood are likewise known, for example, open tank, pressure, paste, spray or brush-coating processes.
Known "classical" wood preservatives based on inorganic compounds are mixtures of chromium and fluorine compounds, the so-called CF salts (see also ULLMANN's Encyklopadie der technischen Chemie [ULLMAN's Encyclopedia of Industrial Chemistry], 4th edition, volume 12, Verlag Chemie, Weinheim 1976, reference Wood Protection, p. 685).
In order to increase the insecticidal action of such agents, arsenic compounds, which are highly toxic to warm-blooded animals, are added (CFA salts). The protective salts mentioned are, for example, mixtures of sodium fluoride and potassium dichromate, optionally with potassium arsenate or sodium arsenate. Readily soluble protective salt mixtures additionally contain potassium hydrogen fluoride.
In these agents, the fluorine and arsenic compounds function as active ingredients against wood-damaging insects and fungi. The chromates and dichromates are neither insecticidally nor fungicidally active, but they are absolutely necessary in order to fix the fluorides in the form of alkali metal chromium fluorides (chromium cryolites) or the arsenates as chromium arsenates. The result is that compounds which are difficult to leach out by water are fixed in the wood in this fashion.
Furthermore, a second, equally important function, namely reduction of corrosion of iron and steel materials by the protective salt solutions, is achieved by the chromium. For fixation and corrosion reduction, considerable, fungicidally and insecticidally ineffective amounts of chromium must be used.
Although the inorganic wood-protection salt mixtures mentioned above are able to protect against damage by a very wide variety of wood-damaging insects and fungi, they provide no protection against wood-rot fungi. For this, treatment with protective salt mixtures which also contain active ingredients against wood-rot fungi is necessary. Known inorganic active ingredients of this type are, in particular, compounds of copper, but also include zinc, nickel and cobalt, and the strong toxins cadmium and mercury.
The necessary fixation in the wood of the components which are active against wood rot is likewise carried out in many known wood preservatives through chromium in the form, for example, of copper chromtes (so-called CC salts), usually together with further insecticidal and fungicidal active ingredients, such as arsenic (CCA) or boron (CCB) or fluorine (CCF salts), see also ULLMANS's Encyclopedia, supra, p. 687. A CCF-salt wood preservative based on complex silicofluorides or boron fluorides, copper salts and ammonium chromate or dichromate is described in German Auslegeschrift No. 1,492,509.
Patent specifications are also known that disclose wood preservatives which act against wood-rot fungi and are based on copper and/or zinc and contain no chromium. German Offenlegungsschrift No. 3,032,463 describes wood preservatives based on copper and/or zinc salts of weak acids, such as acetic, propionic, butyric or other acids, and German Auslegeschrift No. 2,202,448 describes preservatives based on copper, ammonia, carbon dioxide and fatty acids. German Offenlegungsschrift No. 2,418,859 describes wood preservatives based on copper or another amine-forming metal, such as zinc, cobalt or nickel, or based on amine, carbon dioxide and polyphosphates.
German Offenlengungsschrift No. 3,336,557 discloses a wood preservative based on alkali metal or ammonium monofluorophosphates, but this makes an additional component for leaching-resistant fixation in the wood necessary.